Sensor with energy-harvesting device

ABSTRACT

A method of fabricating a device includes forming a moveable plate over a substrate, and forming an energy harvesting coil in the moveable plate. The method further includes forming at least one connector connecting the movable plate with the energy harvesting coil, wherein a portion of the energy harvesting coil extends along the at least one connector. The method further includes forming electrodes around the moveable plate, the electrodes adapted to sense motion of the moveable plate.

PRIORITY CLAIM

The present application is a divisional of U.S. application Ser. No.13/047,502, filed Mar. 14, 2011, which is incorporated by referenceherein in its entirety.

BACKGROUND

Sensors are sometimes placed in locations where there is no power supplyor the power supply is limited by, for example, the battery life orsize. Some Micro-electromechanical systems (MEMS) sensors have a powerconsumption great enough to impact battery life in many applications inwhich the MEMS sensors would be useful. Such MEMS sensors includesensors for detecting position, velocity, acceleration or magneticfields. Applications for such MEMS sensors include, for example,navigation for smart phones.

Kinetic electromagnetic-induction MEMS energy-harvesters convertmechanical energy into electrical energy by converting mechanicalmotion, such as deformation, displacement, velocity, and/oracceleration, of a portion or all of an energy-harvester into electricalcurrent and voltage. The electrical energy is used to power an attacheddevice.

DESCRIPTION OF THE DRAWINGS

One or more embodiments are illustrated by way of example, and not bylimitation, in the figures of the accompanying drawings, whereinelements having the same reference numeral designations represent likeelements throughout and wherein:

FIG. 1 is a device comprising a Lorentz force magnetic sensor andintegrated energy-harvesting functionality according to an embodiment;

FIG. 2 is a device comprising a motion sensor and integratedenergy-harvester according to an embodiment;

FIGS. 3A-3K are cross-sectional views of the device of FIG. 1 or thedevice of FIG. 2 during various stages of manufacturing according to anembodiment;

FIGS. 4A-4K are cross-sectional views of the device of FIG. 1 or thedevice of FIG. 2 during various stages of manufacturing according toanother embodiment; and

FIG. 5 is a high-level functional block diagram of a sensor systemincluding the device of FIG. 1 or the device of FIG. 2 according to anembodiment.

DETAILED DESCRIPTION

FIG. 1 is a device 100 comprising a Lorentz force magnetic sensor 101and an integrated energy-harvester 102 formed within an area of theLorentz force magnetic sensor according to an embodiment. The device 100comprises a substrate 105 with a raised structure 110 and bond pads 112formed on a surface of the substrate. The raised structure 110 comprisesa rectangular-shaped outer portion 115 affixed to the substrate 105 anda rectangular-shaped inner portion 120 free from the substrate butconnected to and formed within the outer portion 115. The inner portion120 is separated from the outer portion 115 by a pair of slots 122formed in the raised structure 110 and around a periphery of the innerportion. The Lorentz force magnetic sensor 101 comprises the innerportion 120, two elastic connections 125, a first wire loop 130 andelectrodes 132. The two elastic connections 125 attach the outer portion115 to the inner portion 120. The elastic connections 125 are formed inthe middle of opposite sides of the inner portion 120, allowing theinner portion to rotate about an axis A defined by the elasticconnections 125.

In at least some embodiments, there are greater or fewer numbers ofelastic connections connecting the inner and outer portions. In at leastsome embodiments, the raised structure 110 and the inner and outerportions 120, 115 comprise different shapes, e.g., square, polygonal,ellipsoid, circular, etc. In at least some embodiments, the innerportion 120 is different shaped from the outer portion 115.

The first wire loop 130 is formed along an outer edge of the innerportion 120. Portions near the two ends of the wire loop 130 are formedon one of the elastic connections 125 so that the wire loop ends areformed on the outer portion 115. On the outer portion 115, the two endsof the first wire loop 130 are connected to pads 135. The pads 135 areconnected (not shown for clarity) by vias formed through the raisedstructure 110 and wiring formed under the raised structure to bond pads112 formed on the substrate 105. The electrodes 132 (positioningindicated by dashed lines) are formed on the substrate 105 underneaththe inner portion 120. The raised structure 110 also comprises theintegrated energy-harvester 102. The integrated energy-harvester 102comprises a second wire loop 145 formed in a spiral loop arrangementinside the first wire loop 130 and a connection wire 150. In at leastsome embodiments, second wire loop 145 comprises a spiral loop having acircular, rectangular, or other shape. A portion of the second wire loop145 near to a first end of the second wire loop is formed on one of theelastic connections 125 so that the first end of the second wire loop isformed on the outer portion 115. A second end of the second wire loop145 is at the center of the inner portion 120 and connected to a firstend of the connection wire 150. The connection wire 150 is formed tocross over the over spiral loops of the second wire loop 145 but doesnot electrically connect to the spiral loops at the crossing points. Aportion of the connection wire 150 near to the second end of theconnection wire is formed on the other of the elastic connections 125 sothat the second end of the connection wire is formed on the outerportion 115. The second end of the connection wire 150 is connected by avia formed through the raised structure 110 and wiring formed the underthe raised structure to bond pads 112. In some embodiments, one elasticconnection 125 is used to connect the inner portion 120 with the outerportion 115. In other embodiments, more than two elastic connections 125are used to connect the inner portion 120 with the outer portion 150.Insome embodiments, the vias formed in the raised structure 110 and thewiring formed under the raised structure connect (not shown for clarity)the Lorentz force magnetic sensor 101 and the integratedenergy-harvester 102 to a circuit formed on the substrate 105.

In operation, an alternating current supplied by a control circuit andpassed around the first wire loop 130 causes a force on the wireproportional to a magnetic field in the vicinity of the first wire loop.In at least some embodiments, the control circuit is formed on thesubstrate 105. A component of the magnetic field in a direction in theplane of the inner portion 120 and perpendicular to the axis A causes anet force on the first wire loop 130 that causes the inner portion 120to rotate about the axis A. Because the current passed around the firstwire loop 130 alternates, the inner portion 120 oscillates back andforth around the axis A. Components of the magnetic field in otherdirections do not cause movement of the inner portion 120. The motion ofthe inner portion is detected capacitively as the inner portion moves bythe electrodes 132. Thus, the Lorentz force magnetic sensor 100 measuresone component of the magnetic field. Additional similar sensorspositioned at different angles enable other components of the magneticfield to be sensed. The Lorentz force magnetic sensor 101 detects, forexample, the magnetic field of the Earth.

The elastic connections 125 also act as return springs causing theposition of the inner portion 120 to return to the plane of the outerportion 115 if no force is applied to the inner portion e.g., via firstwire loop 130. The elasticity of the elastic connections 125 and themass of the inner portion 120 cause the rotation mode of the innerportion to have a resonant frequency corresponding to the elasticity ofthe elastic connections 125 and a mass of the inner portion. If thealternating current frequency is selected to match the resonantfrequency of the inner portion 120, the displacement of the innerportion due to the magnetic field is increased by a quality factor Q ofthe mechanical system formed by the mass of the inner portion 120 andelastic connections 125. Further, the response time to a change in themagnetic field increases by the quality factor Q.

The magnetic field impinging on the first wire loop 130 also passesthrough the spiral of the second wire loop 145 of the integratedenergy-harvester 102. Changes in the magnetic flux enclosed by the areaformed by the second loop 145 induce a voltage across the ends of thesecond loop. The voltage induced is proportional to the rate of changeof the magnetic field coupled to the second loop 145. Thus, movement ofdevice 100 into or out of a magnetic field, rotation of device 100 in amagnetic field or an alternating magnetic field passing through thesensor generated by, for example, power lines carrying alternatingcurrent causes voltage generation across the ends of the second loop145.

Further, if the inner portion 120 moves due to the alternating currentin the first wire loop 130 and an external magnetic field, a voltagewill be induced across the second wire loop 145 by the rotation of theinner portion about the magnetic field.

Independent of how the voltage across the second wire loop 145 isgenerated, the voltage generates a current in the second wire loop. Apower proportional to the product of the voltage across the second wireloop 145 and the current through the second wire loop is extracted fromthe second wire loop and the power provided by the integratedenergy-harvester 102 used to supplement the power for driving theLorentz force magnetic sensor 101. In some embodiments, the powerextracted is sufficient to drive the device 100.

In some embodiments, the power is extracted from the second wire loop145 of the integrated energy-harvester 102 at the same time as ameasurement of the magnetic field passing through the Lorentz forcemagnetic sensor 101. In other embodiments, the power is extracted fromthe second wire loop 145 of the integrated energy-harvester 102 betweenmeasurements of the magnetic field passing through the Lorentz forcemagnetic sensor 101.

FIG. 2 is a device 200 comprising a motion sensor 201 and an integratedenergy-harvester 202 formed within an area of the motion sensoraccording to an embodiment. The device 200 comprises a substrate 205with raised structures and with bond pads 207 formed on a surface of thesubstrate 205. The raised structures comprise an outer portion 210,anchor portions 215 fixed to the substrate 205, a free portion 220 freefrom the substrate and two sets of sense electrodes 222, 224.

The motion sensor 201 comprises the anchor portions 215 the free portion220, the sense electrodes 222, 224, and hairpin springs 225. The freeportion 220 is attached to the anchor portions 215 by the hairpinsprings 225 at corresponding top and bottom edges of the free portionwith respect to the page. The hairpin springs 225 allow the free portionto move relative to the outer portion 210 in a direction along an axis Bdefined by the middle of the two sides of the free portion 220 attachedto the hairpin springs 225. The free portion 220 is also free to movetoward or away from the substrate 205, i.e., into or out of the page.

The free portion 220 comprises fingers 229 that extend away from thesides of the free portion not attached to the hairpin springs 225. Thesense electrodes 222, 224 are formed on either side of the fingers 229,and are attached (not shown for clarity) to the bond pads 207 by viasformed through the raised structures 210, 215, 220, 222, 224 and wiringformed under the raised structures.

In some embodiments, the hairpin springs 225 are replaced by otherelastic structures compatible with embodiments of the disclosure thatallow the free portion 220 to move relative to the outer portion 210 ina direction along an axis B.

The device 200 further comprises the integrated energy-harvester 202formed by a wire loop 230, a portion of a first connection wire 235 anda portion of a second connection wire 240 formed on the free portion220. The wire loop 230 is formed in a spiral arrangement. A first end ofthe wire loop 230 is connected to the first connection wire 235 formedon one of the hairpin springs 225 and connecting across from the freeportion 220 to one of the adjacent anchor portions 215. A second end ofthe wire loop 230 is at the center of the free portion 220 and connectedto a first end of the second connection wire 240. The second connectionwire 240 crosses over the spirals of the wire loop 230 but is notelectrically connected thereto. The second connection wire 240 is formedon the other of the hairpin springs 225 and connects across from thefree portion 220 to the other anchor portion 225. The second end of thefirst and second connection wires 235, 240 are connected (not shown forclarity) via vias formed through the anchor points 225 and wiring formedunder raised structures 210, 215, 220, 222, 224 to the bond pads 207.

In operation, the free portion 220 is displaced relative to thesubstrate 205 when the substrate is accelerated. The mass of the freeportion 220 acts as a proof mass. The proof mass is the mass which isaccelerated by the deformation of the hairpin springs 225 if thesubstrate 205 is accelerated. The displacement relative to the substrateof the proof mass is determined by the acceleration, the elasticity ofthe hairpin springs 225, and the proof mass of the free portion 220. Thedisplacement of the free portion 220 relative to the substrate isdetected by the electrodes 222, 224 by electrostatic sensing. Thus, theacceleration of the motion sensor 201 is measured. In some embodiments,motion of the free portion 220 toward or away from the substrate isdetected by optional electrodes formed on the substrate 205 underneaththe free portion. Additional similar sensors positioned at differentangles, enable other components of the acceleration to be measured.

A magnetic field impinging on the device 200 passes through the spiralof the wire loop 230. The magnetic field can be produced by an optionalpermanent magnet 255. Changes in the total magnetic field passingthrough the area formed by the wire loop 230 cause a voltage to beinduced across the ends of the loop. The voltage induced is proportionalto the rate of change of the magnetic field. Thus, movement into or outof a magnetic field, rotation in a magnetic field or an alternatingmagnetic field generated by, for example, power lines carryingalternating current cause a voltage to be generated across the wire loop230.

Further, motion of the free portion 220 relative to the substrate 205due to acceleration of the device 200 induces a voltage across the wireloop 230 if the motion of the wire loop causes a change in the magneticflux enclosed by the wire loop. In some embodiments, the permanentmagnet 255 is integrated into the device 200 or placed next to thedevice 200 to produce a suitable magnetic field which the wire loop 230moves through when accelerated.

Independent of how the voltage across the wire loop 230 of theintegrated energy-harvester 202 is generated the voltage is used togenerate a current in the second wire loop. A power proportional to theproduct of the voltage across the second wire loop 230 and the currentthrough the second wire loop is extracted from the second wire loop ofthe integrated energy-harvester 202 and used to supplement the power fordriving the device 200. In some embodiments, the power extracted issufficient to drive the device 200.

In some embodiments, the power is extracted from the second wire loop230 at the same time as a measurement of the acceleration of the motionsensor 201. In other embodiments, the power is extracted from the secondwire loop 230 between measurements of the acceleration of the motionsensor 201.

In at least one embodiment, both of the devices 100, 200 described aboveare fabricated using a MEMS process.

FIGS. 3A-3K are cross-sectional views of the device 100 or the device200 during various stage of manufacturing according to an embodiment.

In FIG. 3A, a metal layer 305 is deposited on a substrate 310. The metallayer is fabricated using any process compatible with embodiments of thedisclosure, for example, evaporation, sputtering, chemical vapordeposition or plating. The metal layer 305 comprises, for example, oneor more of copper, gold, silver, nickel, titanium, tantalum, chromium,titanium nitrate, aluminum or alloys thereof.

In FIG. 3B, the metal layer 305 is patterned using any processcompatible with embodiments of the disclosure. The patterning processincludes, for example, coating with photoresist, exposure of thephotoresist through a mask and developing the photoresist. Subsequently,metal exposed through the photoresist is etched using, for example, awet etching process, ion milling, reactive ion milling or plasmaetching. In other embodiments, the metal layer 305 is formed andpatterned by a lift-off process.

The patterned metal layer 305 forms the electrodes 132 and wiring fromthe vias to the bond pads 112 of the device 100 or the wiring, optionalelectrodes on the substrate and bond pads 207 of the device 200.

In FIG. 3C, an oxide layer 315 is formed over the metal layer 310. Theoxide layer 315 is formed by, for example, chemical vapor deposition,sputtering or plasma enhanced chemical vapor deposition. The oxide layer315 is patterned to form depressions 320 using processes similar to oneor more of the photoresist process and etching process used to patternlayer 305.

In FIG. 3D, the oxide layer 315 is further patterned to form pillars 325of differing heights using processes similar to one or more of thephotoresist process and etching process used to pattern layer 305.

In FIG. 3E, a highly doped silicon wafer 330 is fusion bonded to theoxide layer 315. The highly doped silicon wafer 330 is ground down to asuitable thickness, for example, 30 μm. The free portion 220 of device200 and the inner portion 120 of device 100 are ultimately formed fromthe ground highly doped silicon wafer 330. Because the highly dopedsilicon wafer 330 is quite thick compared with the thickness of a layerof polysilicon that it is reasonable to deposit, the free portion 220 ofmotion sensor 201 has a large mass compared with a layer of depositedpolysilicon. Thus, the proof mass formed by the free portion 220 is moremassive and the motion sensor more sensitive than a sensor formed by alayer of deposited polysilicon.

In FIG. 3F, the ground silicon wafer 330 is patterned and etched in oneor more etch processes to form through-holes 335, trenches 340 andpillars 345. The patterning and etching processes similar to one or moreof the photoresist process and etching process used to pattern layer305.

In FIG. 3G, the through-holes 335 and trenches 340 are filled with aelectrical insulating materials, for example silicon dioxide, andconducting material 360, for example, titanium nitrate and tungstenusing, for example, a chemical vapor deposition and polishing process.The material in the trenches forms the first and second wire loops 130,145 of the device 100 and the wire loop 230 of the device 200 and thevias connecting the first and second wire loops 130, 145 and the wireloop 230 to the bond pads 112, 207.

In FIG. 3H, insulation material 365, for example, silicon dioxide orsilicon nitride is formed over the ground silicon wafer and theconducting material 360. Over the patterned insulation material 365,wiring 370 is formed. The wiring 370 corresponds to connection wire 150of the device 100 and the first and second connection wires 235, 240 ofthe device 200.

In FIG. 3I, slots 375 are etched through the ground silicon wafer 330.The slots 375 delineate the inner portion 120 and the elasticconnections 125 of the device 100 and the hairpin springs 225, anchorportions 215, free portion 220 and electrodes 222, 224 of the device200.

In FIG. 3J, a capping wafer 380 is bonded to portions of the metal 305that form a bonding ring around the device 100 and the device 200.

In FIG. 3K, an optional hard magnetic layer 385 is coated on thebackside of the substrate 310 and a top surface of the capping wafer380. The optional hard magnetic layer 385 is magnetized so that thefield generated by the permanent magnet formed by the magnetizedmagnetic layer 385 causes current generation in the second wire loop 145or the wire loop 230 if the second wire loop 145 or the wire loop 230moves relative to the magnetic field.

FIGS. 4A-4L are cross-sectional views of the device 100 or the device200 at various stages of manufacturing according to another embodiment.

In FIG. 4A, insulating layers 405 are deposited on a top surface and abottom surface of a substrate 410. Insulating layers 405 are formedfrom, for example, silicon oxide or silicon nitride by, for example,chemical vapor deposition, sputtering or in the case of silicon oxide bythermal growth. Top and bottom metal layers 407 a/407 b are formed onthe insulating layers 405. The metal layer 407 is fabricated using anyprocess compatible with embodiments of the disclosure, for example,evaporation, sputtering, chemical vapor deposition or plating. The metallayers 407 a/407 b comprise, for example, one or more of copper, gold,silver, nickel, titanium, tantalum, chromium, titanium nitrate, aluminumor alloys thereof.

In FIG. 4B, top metal layer 407 a is patterned and etched usingprocesses similar to one or more of the photoresist process and etchingprocess used to pattern layer 305.

In other embodiments, the metal layer 407 a is formed and patterned by alift-off process. In other embodiments, metal layers 407 a and 407 b arepolysilicon.

The patterned top metal layer 407 a forms the electrodes 132 and wiringfrom the vias to the bond pads 112 of the device 100 or the wiring,optional electrodes on the substrate and bond pads 207 of the device200.

In FIG. 4C, an oxide layer 415 is formed over the top metal layer 407 a.The oxide layer 415 is formed by, for example, chemical vapordeposition, sputtering or plasma enhanced chemical vapor deposition.

In FIG. 4D, polysilicon layer 420 is deposited on the oxide layer 415.The free portion 220 of the device 200 and the inner portion 120 ofdevice 100 are ultimately formed from the polysilicon layer 420.

In FIG. 4E, the polysilicon layer 420 is patterned and etched in one ormore etch processes to form through-holes 425 and trenches 430 usingprocesses similar to one or more of the photoresist process and etchingprocess used to pattern layer 305.

In FIG. 4F, the through-holes 425 and trenches 430 are filled with aconducting material 435, for example, titanium nitrate and tungstenusing, for example, a chemical vapor deposition and polishing process.The material in the trenches forms the first and second wire loops 130,145 of the device 100 and the wire loop 230 of the device 200 and thevias connecting the first and second wire loops 130, 145 and the wireloop 230 to the bond pads 112, 207.

In embodiments in which 407 a and 407 b are polysilicon, the oxide layer415 is deposited and patterned to form the through-holes 425.Polysilicon is deposited over the oxide layer 415 to form a continuouspolysilicon layer 420. The continuous polysilicon layer is subsequentlypatterned to form trenches 430. The conductive material 435 are formedin the trenches 430.

In FIG. 4G, insulation material 440, for example, silicon dioxide orsilicon nitride is formed over the polysilicon layer 420 and theconducting material 435. The insulation material 440 is patterned andetched using processes similar to one or more of the photoresist processand etching process used to pattern layer 305. Over the patternedinsulation material 440, wiring 445 is formed. The wiring 445corresponds to connection wire 150 of the device 100 and the first andsecond connection wires 235, 240 of the device 200.

In FIG. 4H, slots 450 are etched through the polysilicon layer 420. Theslots 450 delineate the inner portion 120 and the elastic connections125 of the device 100 and the hairpin springs 225, anchor portions 215,free portion 220 and electrodes 222, 224 of the device 200.

In FIG. 4I, portions 455 of the oxide layer 415 are etched via the slots450 by, for example, an HF vapor etch or a buffered HF wet etch.

In FIG. 4J, a bonding ring 460 is formed and patterned on top ofpolysilicon layer 420 using processes similar to one or more of thephotoresist process and etching process used to pattern layer 305.

In other embodiments, the bonding ring 460 is formed and patterned bylift-off process. In some embodiments, the bonding ring 460 is formedand patterned at the same time as forming wiring 445 or immediatelyafter formation of wiring 445.

In FIG. 4K, a capping wafer 465 is bonded to the bonding ring 460 aroundthe device 100 or the device 200.

An optional hard magnetic layer 385 (FIG. 3K) is coated on the backsideof the substrate 410 over bottom metal layer 407 b and a top surface ofthe capping wafer 465. The optional hard magnetic layer 385 ismagnetized so that the field generated by the permanent magnet formed bythe magnetized magnetic layer 385 causes current generation in thesecond wire loop 145 or the wire loop 230 if the second wire loop 145 orthe wire loop 230 moves relative to the magnetic field.

In both of the processes depicted in FIGS. 3A-3K and 4A-4K the cappingwafer 380, 465 and the bonding rings form a seal that protects thedevice 100 and the device 200 from the environment.

FIG. 5 is a functional diagram of a sensor system 500 according to anembodiment. Sensor system 500 comprises a MEMS sensor 505, a controller510, signal processing electronics 515 and an optional permanent magnet520. The MEMS sensor 505 comprises one or more MEMS sensors withenergy-harvester 100, 200 described above. The controller 510 controlsthe MEMS sensor 505 and collects energy from the energy-harvester,redistributing the collected energy to the MEMS sensor 505 and thesignal processing electronics 515, thus reducing the power consumptionof the sensor system. In some embodiments, the MEMS sensor 505 is on thesame substrate as a substrate on which the controller 510 and signalprocessing electronics 515 is formed. In some embodiments, thecontroller 510 and signal processing electronics 515 are formed on thesubstrate beneath the MEMS sensor 505. In some embodiments, thecontroller 510 and signal processing electronics 515 are formed on thesame substrate as the MEMS sensor 505 but in a different portion of thesubstrate, either at the same side or a different side from the sidewhere the sensor is formed. In other embodiments, the controller 510 andsignal processing electronics 515 for the sensor system 500 are formedon a separate substrate and wire bonded or die bonded to the substratewith the MEMS sensor 505. The optional permanent magnet 520 produces amagnetic field for the energy-harvester of the MEMS sensor 505.

One aspect of this description relates to a method of fabricating adevice. The method includes forming a moveable plate over a substrate,and forming an energy harvesting coil in the moveable plate. The methodfurther includes forming at least one connector connecting the movableplate with the energy harvesting coil, wherein a portion of the energyharvesting coil extends along the at least one connector. The methodfurther includes forming electrodes around the moveable plate, theelectrodes adapted to sense motion of the moveable plate.

Another aspect of this description relates to a method of fabricatingenergy harvesting device. The method includes bonding a silicon wafer toa substrate, and patterning the bonded silicon wafer to form a moveableplate. The method further includes patterning the bonded silicon waferto form an energy harvesting coil. The method further includespatterning the bonded silicon wafer to form at least one connectorconnecting the movable plate with an outer portion of the bonded siliconwafer, wherein a portion of the energy harvesting coil extends along theat least one connector. The method further includes forming electrodeson the substrate, wherein the electrodes adapted to sense motion of themoveable plate.

Still another aspect of this description relates to a method offabricating energy harvesting device. The method includes forming apolysilicon layer over a substrate, and patterning the polysilicon layerto form a moveable plate. The method further includes patterning thepolysilicon layer to form an energy harvesting coil. The method furtherincludes patterning the polysilicon layer to form at least one connectorconnecting the movable plate with an outer portion of the polysiliconlayer, wherein a portion of the energy harvesting coil extends along theat least one connector. The method further includes forming electrodeson the substrate, wherein the electrodes adapted to sense motion of themoveable plate.

It will be readily seen by one of ordinary skill in the art that thedisclosed embodiments fulfill one or more of the advantages set forthabove. After reading the foregoing specification, one of ordinary skillwill be able to affect various changes, substitutions of equivalents andvarious other embodiments as broadly disclosed herein. It is thereforeintended that the protection granted hereon be limited only by thedefinition contained in the appended claims and equivalents thereof.

What is claimed is:
 1. A method of fabricating a device comprising:forming a moveable plate over a substrate; forming an energy harvestingcoil in the moveable plate; forming at least one connector connectingthe movable plate with the energy harvesting coil, wherein a portion ofthe energy harvesting coil extends along the at least one connector; andforming electrodes around the moveable plate, the electrodes adapted tosense motion of the moveable plate.
 2. The method of claim 1, furthercomprising: forming at least one spring or hinge to attach the moveableplate to the substrate; and forming wiring connecting theenergy-harvesting coil to at least one of a bond pad or a controlcircuit formed on the substrate.
 3. The method of claim 1, whereinforming the moveable plate comprises fusion bonding a silicon wafer tothe substrate.
 4. The method of claim 3, wherein fusion bonding thesilicon wafer comprises depositing an oxide layer over the substrate andfusion bonding the silicon wafer to the oxide layer.
 5. The method ofclaim 3, wherein forming the movable plate further comprises reducing athickness of the fusion bonded silicon wafer.
 6. The method of claim 1,wherein forming the movable plate comprises forming a polysilicon layerover the substrate.
 7. A method of fabricating energy harvesting device,the method comprising: bonding a silicon wafer to a substrate;patterning the bonded silicon wafer to form a moveable plate; patterningthe bonded silicon wafer to form an energy harvesting coil; patterningthe bonded silicon wafer to form at least one connector connecting themovable plate with an outer portion of the bonded silicon wafer, whereina portion of the energy harvesting coil extends along the at least oneconnector; and forming electrodes on the substrate, wherein theelectrodes adapted to sense motion of the moveable plate.
 8. The methodof claim 7, wherein bonding the silicon wafer to the substrate comprisesfusion bonding the silicon wafer to the substrate.
 9. The method ofclaim 8, wherein fusion bonding the silicon wafer to the substratecomprises: forming an oxide layer over the substrate; and fusion bondingthe silicon wafer to the oxide layer.
 10. The method of claim 7, whereinforming the electrodes comprises: forming a conductive layer over thesubstrate; and patterning the conductive layer to form the electrodes.11. The method of claim 10, further comprising forming a through openingin the bonded silicon wafer, wherein the through opening exposes aportion of the conductive layer.
 12. The method of claim 11, furthercomprising bonding a cap wafer to the substrate, wherein the cap wafercomprises a protrusion contacts the exposed portion of the conductivelayer.
 13. The method of claim 12, further comprising forming a hardmagnetic layer on a surface of the cap wafer opposite the substrate. 14.The method of claim 7, further comprising forming a hard magnetic layeron a surface of the substrate opposite the bonded silicon wafer.
 15. Amethod of fabricating energy harvesting device, the method comprising:forming a polysilicon layer over a substrate; patterning the polysiliconlayer to form a moveable plate; patterning the polysilicon layer to forman energy harvesting coil; patterning the polysilicon layer to form atleast one connector connecting the movable plate with an outer portionof the polysilicon layer, wherein a portion of the energy harvestingcoil extends along the at least one connector; and forming electrodes onthe substrate, wherein the electrodes adapted to sense motion of themoveable plate.
 16. The method of claim 15, wherein forming theelectrodes comprises: forming a first conductive layer over thesubstrate; and patterning the first conductive layer to form theelectrodes.
 17. The method of claim 16, further comprising forming asecond conductive layer over a surface of the substrate opposite thefirst conductive layer.
 18. The method of claim 15, further comprisingforming an insulator layer over the substrate between the substrate andthe polysilicon layer, wherein patterning the polysilicon layer to formthe moveable plate comprises: exposing a first portion of the insulatorlayer through the polysilicon layer; removing a second portion of theinsulator layer between the substrate and the polysilicon layer.
 19. Themethod of claim 15, further comprising bonding a capping wafer to thepolysilicon layer.
 20. The method of claim 19, wherein bonding thecapping wafer to the polysilicon layer comprises: forming a bonding ringon the polysilicon layer; and bonding the capping wafer to the bondingring.